Classifications

• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F5/00—Compounds of magnesium
  • C01F5/26—Magnesium halides
  • C01F5/30—Chlorides
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
  • C01F5/00—Compounds of magnesium
  • C01F5/02—Magnesia
  • C01F5/06—Magnesia by thermal decomposition of magnesium compounds
  • C01F5/10—Magnesia by thermal decomposition of magnesium compounds by thermal decomposition of magnesium chloride with water vapour
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/60—Particles characterised by their size
  • C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer

Definitions

• the invention relates to a process for the production of pure magnesium oxide, particularly suitable for the production of refractory products, from magnesium silicate and magnesium hydrosilicate materials, such as olivine, serpentine, garnierite or the like, the starting material being digested with hydrochloric acid, the residues remaining in the process the digestion sludge is separated off and the sesquioxide and other impurities to be regarded as impurities are precipitated from the crude brine thus obtained, the addition of a pH-increasing substance, the precipitates are separated off and the magnesium chloride solution thus obtained is subjected to thermal decomposition, in particular by spray roasting, in which Magnesium oxide is obtained and hydrogen chloride is recovered.
• magnesium silicate and magnesium hydrosilicate materials such as olivine, serpentine, garnierite or the like
• the starting material for this process are the so-called ultramafitic rocks of the group peridotite, dunite, resinburgite and the like Waste products of a similar composition are considered, provided that they have an MgO content of at least 15% by weight. These materials are summarized below under the name “serpentine” or "raw serpentine”.
• magnesium oxide is generally used as the pH-increasing substance for precipitating the sesquioxides, mostly in the form of caustic burned magnesia.
• the use of this precipitant has disadvantages.
• the serpentines and similar starting materials are generally high in iron and others Sesquioxide impurities and large amounts of precipitant are required. Since all types of caustic magnesia are expensive because they can only be produced with considerable effort, in particular with thermal energy, the use of caustic magnesia as a precipitant results in a great economic burden.
• the pure magnesium oxide obtained as the end product of the process is used as a precipitant, depending on the content of iron and other sesquioxide impurities in the raw serpentine or similar starting material, up to about 30% by weight of the magnesium oxide obtained is to be conducted in an internal cycle, which is not economically justifiable is.
• the object of the invention is to provide a method of the type mentioned at the outset in which the disadvantages mentioned are avoided and which enables economical operation and the formation of readily filterable hydroxide precipitates.
• the inventive method of the type mentioned is characterized in that the pH-increasing substance used to precipitate the oxides of iron and aluminum finely ground raw serpentine with a grain size of 0 to 1 mm, preferably 0 to 0.1 mm.
• divalent iron is present in the starting material and this divalent iron is also to be removed, air and / or another oxidizing agent, such as chlorine or hydrogen peroxide H 2 O 2, can be intensively, according to an embodiment of the process according to the invention for converting the divalent iron to precipitable trivalent iron Introduce the raw brine into it.
• divalent manganese is present in the starting material and is to be removed, this must be converted into tetravalent manganese by oxidation. This can take place in the course of an oxidation treatment which is carried out for converting divalent iron into trivalent iron; an oxidation treatment supplementing the oxidation treatment of iron can also be carried out for the oxidation of the manganese.
• the precipitation taking place in the process according to the invention can be carried out either batchwise or continuously.
• One of the advantages of the method according to the invention is that the starting material only has to be comminuted, but otherwise does not need to be pretreated, in particular does not need to be fired.
• the precipitation process proceeds in the following manner: initially, after adding the raw serpentine to the from the Digestion sludge obtained by removing the undissolved digestion residue gives the pH of the raw brine rapidly up to about 4, which favors the oxidation of the iron, which is initially still divalent in the acidic raw brine, to the trivalent form of iron; this in turn entails a relatively rapid precipitation of contaminants at the beginning of the entire process. Later, the pH value drops somewhat as a result of the oxidation of Fe++ to Fe +++ , and then rises again. This increase in pH is steady and slow, with the pH remaining below 5.
• the crude serpentine used as the precipitant is added in an amount of the crude brine which is between 1 1/2 and 2 1/2 times the stoichiometric requirement.
• the stoichiometric requirement is the quantity of raw serpentine whose MgO content is sufficient to neutralize the acidity of the raw brine; the acidity of the crude brine is given by the amount of free HC1 present in the acidic crude brine and by the content of the crude brine in the precipitation accessible oxidic impurities, both the oxidic impurities which were present in the crude brine before the addition of the raw serpentine serving as precipitant , and also the oxidic impurities which have been introduced into the raw brine with the raw serpentine serving as a precipitant must be taken into account.
• the temperature of the raw brine is kept above 80 ° C. for the precipitation of impurities caused by adding raw serpentine to the raw brine.
• a further advantageous embodiment of the method according to the invention is characterized in that after the completion of the precipitation of impurities caused by the addition of raw serpentine to the raw brine, any iron as well as manganese, nickel and others remaining in the brine are present in the brine Sesquioxide impurities are precipitated in a known manner by adding known, pH-increasing substances, preferably caustic magnesia or a fly dust accumulating during magnesite burning.
• a variant of this embodiment is characterized in that the precipitation carried out by adding raw serpentine to the raw brine at a pH below 5 only leads to the precipitation of the majority of the iron and aluminum hydroxide and that the precipitation process is then carried out by increasing the pH -Values to 6 to 7 quickly finish using a small amount of caustic magnesia.
• Example 1 1730 kg of raw serpentine, which contained 728 kg of MgO, 122 kg of Fe203, 4.66 kg of NiO and 5 kg of CaO, were broken down with 7330 kg of hydrochloric acid, which had a content of 1330 kg of Cl ⁇ . An insoluble digestion residue in the amount of about 710 kg was separated from the pulping slurry and 8350 kg of acidic raw brine were obtained in this way.
• This crude brine which contained 713 kg MgO, 113 kg Fe203, 4.6 kg NiO, 1330 kg Cl ⁇ and 1.8 kg CaO, was mixed with 647 kg raw serpentine in the grain size from 0 to 0.1 mm as a precipitant and it air was passed into the crude brine, the temperature of which was kept above 80 ° C., with intensive stirring. The pH rose to about 4 and the precipitation was complete after several hours.
• the precipitated material was separated off together with the undissolved portions of the raw serpentine added as a precipitant, resulting in a filter cake weighing 823 kg.
• the filter cake contained 225 kg MgO, 157 kg Fe2O3, 1 kg NiO and 1.4 kg CaO.
• the remaining pure brine contained 748 kg MgO, 0.08 kg Fe2O3, 5.15 kg NiO, 1324 kg Cl and 3 kg CaO.
• Example 2 1585 kg of raw serpentine, which contained 667 kg of MgO, 112 kg of Fe2O3, 4.27 kg of NiO and 4.59 kg of CaO, were broken down with 6746 kg of hydrochloric acid, which had a content of 1220 kg of Cl ⁇ . An insoluble digestion residue in the amount of about 625 kg was separated from the digestion slurry and 7706 kg of crude acid brine was obtained.
• This crude brine which contained 643 kg of MgO, 104 kg of Fe2O3, 4.20 kg of NiO, 1220 kg of Cl ⁇ and 1.8 kg of CaO, was mixed with 597 kg of raw serpentine in a grain size of 0 to 0.1 mm as a precipitant and it air was passed into the crude brine, the temperature of which was kept above 80 ° C., with intensive stirring.
• the pH rose to approx. 4 and was quickly raised to pH 6.8 after 4 hours of reaction by adding 98 kg of flying dust.
• the flying dust contained 82 kg MgO, 5.20 kg Fe203 and 2.60 kg CaO. As a result, the precipitation could be completely completed within 1 hour.
• the precipitated material was separated off together with the undissolved portions of the precipitants raw serpentine and caustic magnesia, resulting in a filter cake of 830 kg. It contained 255 kg MgO, 145 kg Fe2O3, 1.85 kg CaO and 4.27 kg NiO.
• the remaining pure brine (7571 kg) contained 721 kg MgO, ⁇ 0.01 kg Fe2O3, 4.25 kg Ca0, ⁇ 0.01 kg NiO and 1210 kg Cl ⁇ .

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Thermal Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Geology (AREA)
• Inorganic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
• Manufacture And Refinement Of Metals (AREA)
• Silicates, Zeolites, And Molecular Sieves (AREA)
• Solid-Sorbent Or Filter-Aiding Compositions (AREA)
• Compositions Of Oxide Ceramics (AREA)
• Compounds Of Iron (AREA)
• Vessels, Lead-In Wires, Accessory Apparatuses For Cathode-Ray Tubes (AREA)
• Nitrogen Condensed Heterocyclic Rings (AREA)
• Joints With Sleeves (AREA)

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• 1988
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